.\" Copyright (c) 1991, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" Processing Systems.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)atof.3	8.1 (Berkeley) 6/4/93
.\" $FreeBSD: src/lib/libc/stdlib/atof.3,v 1.17 2007/01/09 00:28:09 imp Exp $
.\"
.Dd June 4, 1993
.Dt ATOF 3
.Os
.Sh NAME
.Nm atof ,
.Nm atof_l
.Nd convert
.Tn ASCII
string to double
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In stdlib.h
.Ft double
.Fn atof "const char *str"
.In xlocale.h
.Ft double
.Fn atof_l "const char *str" "locale_t loc"
.Sh DESCRIPTION
The
.Fn atof
function converts the initial portion of the string pointed to by
.Fa str
to
.Vt double
representation.
.Pp
It is equivalent to:
.Bd -literal -offset indent
strtod(str, (char **)NULL);
.Ed
.Pp
The decimal point
character is defined in the program's locale (category
.Dv LC_NUMERIC ) .
.Pp
While the
.Fn atof
function uses the current locale, the
.Fn atof_l
function may be passed a locale directly. See
.Xr xlocale 3
for more information.
.Sh IMPLEMENTATION NOTES
The
.Fn atof
and
.Fn atof_l
functions are thread-safe and async-cancel-safe.
.Pp
The
.Fn strtod 
and 
.Fn strtod_l
functions are recommended instead of 
.Fn atof
and
.Fn atof_l
functions, especially in new code.
.Sh ERRORS
The function
.Fn atof
need not affect the value of
.Va errno
on an error.
.Sh SEE ALSO
.Xr atoi 3 ,
.Xr atol 3 ,
.Xr strtod 3 ,
.Xr strtol 3 ,
.Xr strtoul 3 ,
.Xr xlocale 3
.Sh STANDARDS
The
.Fn atof
function conforms to
.St -p1003.1-90 ,
.St -isoC ,
and
.St -isoC-99 .
